Hi I followed the recommendation from smteinturs above. I am on a Linux system. This did not work for me. Sad! :(

Update: My bad -- It does work -- I had been trying to add a link to a PDF and that was what was not working. The Zotero documentation suggested to just download the PDF and then drag that into the main window in the Zotero app (not the Browser extension). That worked so I am back in business. Sorry for the confusion.